The invention relates to the field of intravascular delivery systems, and more particularly to balloon designs for drug delivery.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guide wire, positioned within an inner lumen of an dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guide wire crosses a lesion to be dilated. Then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient""s coronary anatomy, over the previously introduced guide wire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) so that the stenosis is compressed against the arterial wall and the wall expanded to open up the passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
After angioplasty procedures, restenosis may form in the artery at the original stenotic site, necessitating either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion.
At times during the angioplasty procedure or the stent delivery, it is desirable to deliver therapeutic agents specifically in the stenoic regions of the patient""s coronary under treatment.
Therefore, what has been needed are balloons with improved design for the specific delivery of therapeutic agents during angioplasty or stent delivery. The present invention satisfies these and other needs.
The invention is directed to an inflatable member for delivery of therapeutic agents to a desired site within a patient""s body, in particular, balloons for use with balloon catheters and stent delivery systems; and balloon catheters and stent delivery systems including the same; and methods for making and using the same.
The inflatable member of the present invention includes proximal and distal sections and an intermediate section longitudinally disposed therebetween. The balloon has an outer layer defining an outer wall of the inflatable member and an inner layer extending along at least a portion of the longitudinal dimension of the outer layer and forming a fluid tight seal with the outer layer at the proximal and distal sections. The outer and inner layers define an outer chamber therebetween for housing the therapeutic agent. The outer layer, at the portion which in part defines the outer chamber, includes apertures for delivering the therapeutic agent onto or about the site, upon inflation of the balloon. The inner layer defines, at least in part, a balloon interior chamber configured for fluid communication with at least a portion an elongated member, such as an inflation lumen of a balloon catheter.
In another embodiment, the inner layer also includes inner apertures for delivering pressurized bio-compatible fluid to the outer chamber. In a preferred embodiment, the inner apertures are set off from the outer apertures to enhance the mixing of the therapeutic agents as they are being released from the outer apertures.
The therapeutic agent may be a viscous agent, as for example in the form of a solid, powder, or simply a viscous liquid; or a non-viscous liquid. The therapeutic agent can be housed in the outer chamber, or in the alternative applied onto an inner surface of the outer chamber for future release onto or about the site.
When the therapeutic agent is a liquid, either or both embodiments with or without the inner layer apertures, can be used.
In the embodiment having inner apertures in the inner layer, the liquid agent, preferably, is viscous, such that it will not flow back into the balloon interior chamber through the inner layer apertures. In the alternative or in combination with the viscous liquid, the material for constructing the inner layer is such that the liquid agent once in the outer chamber is not permeable through the inner layer apertures. Upon introduction of a pressurized bio-compatible fluid (e.g., saline) into the balloon interior chamber, the fluid enters the outer chamber, mixes with the agent and is released through the outer layer apertures.
Preferably, when a viscous agent (e.g., solid, powder, or viscous liquid) is used, the inner layer, includes the inner layer apertures, and the agent is delivered to the site as described above.
In the alternative, the agent may be non-viscous. As such, the agent is released from the outer layer apertures when inflation fluid is directed to the balloon interior chamber through shaft inflation lumen. As the balloon interior chamber expands, the inner layer applies pressure onto the agent within the outer chamber releasing the agent through the outer layer apertures.